In the clinical laboratory environment, there is an ongoing intensive effort to develop instruments for performing or analyzing the clinical assays performed. Instrumentation and automation in the chemistry and hemotology clinical laboratory has outpaced the instrumentation and automation in the microbiology lab.
Two areas of microbiological testing in the clinical laboratory are identifying microbes such as bacteria and determining minimum inhibitory concentrations or MIC values of antimicrobial agents. The instruments that are used for determining MIC values generally use a light source and some means for measuring light passing through a cell wherein a particular specimen has been allowed to react and incubate with a known antimicrobial agent. Depending upon whether the light is scattered, absorbed, reflected, or passed through the cell, the MIC values can be determined. Similarly, instruments for identifying microbes can use the same technique of measuring whether light is passed through a cell containing a particular specimen and the necessary identifying reagents.
One system for identifying bacteria and determining MIC values is disclosed in U.S. Pat. No. 4,448,534, issued May 15, 1984, to Wertz, Hathaway, and Cook, the entire disclosure of which is incorporated herein by this reference. In that patent, an automatic scanning apparatus for performing optical density tests on liquid samples, as well as methods for testing for antibiotic susceptibility and identifying microorganisms, is disclosed. The apparatus includes a system for automatically, electronically scanning each well of a multi-well tray containing many liquid samples. A light source is passed through the cells to an array of photosensitive cells corresponding to each well in the tray. Within the tray, there is a calibrating or comparison cell. Electronic apparatus reads each cell in sequence, quickly completing the scan without physical movement of any parts. The resultant signals are compared with the signals from a comparison cell and with other signals of stored data and determinations are made and can be displayed or printed out.
A system of the type described in the patent is sold by the American MicroScan division of American Hospital Supply Corporation, and commonly referred to as the autoSCAN-3 (trademark of American Hospital Supply Corporation) susceptibility instrument and its successor instrument, an autoSCAN-4 susceptibility instrument. A predecessor instrument provided a light source which illuminated each cell of the tray and an attendant visually inspected each cell and noted on a provided recording chart whether there was growth (turbidity) or no-growth (clear) in each cell.
Another predecessor instrument which is commercially available is an MIC determining instrument, also sold by the American MicroScan division of American Hospital Supply Corporation and identified as the touchSCAN (trademark of American Hospital Supply Corporation) susceptibility instrument. The instruments utilize a tray or panel containing an array of wells in each of which a determination is being conducted. In the touchSCAN instrument, the panel is placed within a panel receiving slot which is covered by a plurality of touch sensitive switches corresponding to each of the cells or wells in the panel. A light source in the instrument is activated and based upon the user's viewing of each of the cells in the panel, the appropriate touch-sensitive switch is activated by the user. The touch-sensitive switch sends an electrical signal to a microprocessor which can record and store the data and identifying values for each cell for which the signal has been generated.
It would be desirable to provide an instrument which could receive trays and panels and which can be readily read by simple actuation which readily and specifically identifies a given cell in the array of cells on the panel. In addition, it would be desirable to provide an instrument which could make such identifications without regard to the width and length of a panel and without regard to the number of cells on the array on the panel. It would also be desirable to provide an instrument in which the operator would have a clear view of each well and wherein the operator would not have to look through a hole in the switch matrix. It would also be desirable to provide an instrument which would not require special overlays and wherein identifying indicia can be placed directly on the panel and read directly by the operator during analysis. It would also be desirable to provide an instrument which could read a variety of trays without the need to provide different well locations and which instrument could be programmed for the geometry of differing panels to identify and locate particular cells within the array of a particular panel.